synaptic transmission

• Synaptic transmission


  1. Action potential reaches terminal buttons

  2. Neurotransmitters released from synaptic vesicles into synaptic gap

  3. Neurotransmitters bind to postsynaptic receptor sites

  4. Re-uptake of neurotransmitters back into presynaptic neuron

  5. Enzymes 'turn off' neurotransmitters
• Neurotransmitters


  Chemicals that diffuse across the synapse to the next neuron
• Neurotransmitter receptor sites


  • Only 'fit' certain neurotransmitters, precisely tailored to match the shape of the neurotransmitters
• Excitatory neurotransmitters


  Action potential travels along the next neuron
• Excitation


  Leads to a neuron becoming positively charged and more likely to fire
• Excitatory neurotransmitter


  • Noradrenaline
• Inhibition


  Leads to a neuron becoming more negatively charged and less likely to fire
• Inhibitory neurotransmitter


  • Serotonin
• GABA is purely inhibitory
• Each neuron can have hundreds of dendrites and terminal buttons
• A single neuron can be 'in touch' with many other neurons at both its input (dendrites) and output (terminal buttons)
• The decision to 'fire' or not depends on the combined/summed effects of all the neurons with which a receiving neuron forms synapse
• If the number of excitatory neurotransmitters are the same as the number of inhibitory neurotransmitters, they cancel each other out and the neuron does not fire
• Synaptic transmission


  1. Action potential reaches terminal buttons

  2. Neurotransmitters released from synaptic vesicles into synaptic gap

  3. Neurotransmitters bind to postsynaptic receptor sites

  4. Re-uptake of neurotransmitters back to presynaptic neuron

  5. Enzymes 'turn off' neurotransmitters
• Synapse


  The gap between two neurons
• Neurotransmitters


  Chemicals that diffuse across the synapse to the next neuron
• Receptor sites


  Only 'fit' certain neurotransmitters, precisely tailored to match the shape of the neurotransmitters
• Enough excitatory neurotransmitters


  Action potential travels along the next neuron
• Re-uptake


  Neurotransmitter returns back to the presynaptic neuron, where it is stored ready for later release
• Enzymes


  'Turn off' a neurotransmitter after they have stimulated a post synaptic neuron, making the neurotransmitter ineffective
• Neurotransmitters


  • Can have an excitatory or inhibitory effect on the next neuron
  • GABA is purely inhibitory
• Excitation


  Leads to a neuron becoming positively charged and more likely to fire
• Inhibition


  Leads to a neuron becoming more negatively charged and less likely to fire
• Neuron


  • Can have hundreds of dendrites and terminal buttons
  • Can be 'in touch with many other neurons at both its input (dendrites) and output (terminal buttons)
• Number of excitatory neurotransmitters = number of inhibitory neurotransmitters


  They cancel each other out and the neuron does not fire